Device for feeding additional materials into a stream of molten metals



Dec. l2, 1967 H. BAKKERUS 3,357,692

DEVICE FOR FEEDING ADDITIONAL MATERIALS INTO A STREAM 0F MOLTEN METALS Filed oct. 5, 1964 INVENTOR.

HER ANUS BAKKE US BY/m ATTORNEYS United States Patent Office 3,357,692 Patented Dee. l2, i967 3,357,6@2 DEVKCE FR FEEDTNG ADDTTHNAL MATERIALS TNT() A STREAM F MQLTEN METALS Hermanus Bakkerns, Voorburg, Netherlands, assignor to Nederlandse Organisatie voor Toegepast-Natuurwetenschappelijk Onderzoek ten behoeve van Nijverheid, Handel en Verkeer, The Hague, Netherlands, a corporation of the Netherlands Filed Get. 5, 1964, Ser. No. 40l,612 Claims priority, application Netherlands, Oct. 14, 1964, 299,266 7 Claims. (Cl. 266-39) ABSTRACT F THE DSCLOSURE A device for feeding additives into a stream of molten metals in which there is a mouthpiece in the bottom of the storage chamber for the melt. The mouthpiece includes an outlet channel having a transverse cross section which gradually decreases toward the outlet, and a cylindrical feeding chute is mounted concentrically within the outlet.

This invention relates to a device for feeding additive materials into a stream of molten metals, which additive materials have lower boiling points and/ or specific weights than the molten metals. More particularly, the invention is concerned with such a device for feeding magnesium or preliminary alloys thereof into a stream of molten iron for the preparation of nodular cast iron.

In alloying, magnesium and its allied metals present many problems, particularly so, because magnesium, for instance, will melt at 650 C. and will boil at 1120" C.

This is not only because, when fed into a melt having a higher temperature, they will prematurely evaporate and oxidize before they can be absorbed into the melting bath, but also because, due to their own low specific weight and to the high surface tension of the liquid metal, it is extremely difficult for them to penetrate into the bath. They are partially thrown back towards the bath surface, and as to that part which is eventually absorbed into the bath it is particularly diflicult to obtain a homogeneous distribution in the cast iron products. Moreover, in consequence of the rapid evaporation and oxidation, there is a risk of great quantities of iron spattering away as well as a risk of explosions, which, besides being dangerous to the attendant personnel, renders the attainment of the required composition almost impossible.

A great many measures for obviating these problems have already been proposed. The additive material(s) may be placed on the bottom of a -ladle and the liquid metal may be poured on to it (them). In a filled ladle, the additional material may be introduced by means of an immersion body, it may be thrown vigorously on to the bath by means of a rapidly revolving paddle wheel or it may be strewn on the bath surface and stirred in very intensively.

Further, the feeding in may be effected, while filling a ladle by dropping the additional material from a great height on to a stream of molten metals, or by adding it gradually on or in the stream.

In applying these methods use is often made of an airtight closed space or of a protective gas atmosphere under high pressure in order to prevent evaporation and oxidation. Further, a gas may be used as a carrier for the additional materials. Thus, pure magnesium can only be introduced in the bottom part of the molten mass, carried on a nitrogen stream, or on top of the molten mass in a closed oit space under a pressure of about 4.5-7 atmospheres.

All these methods have their own specific advantages but also their Very great diiculties, particularly because the useful effect of the treatment often is very small. By way of example we will now describe two devices, which are Vused in feeding additional material into a stream of molten metals and which come nearest to the device according to this invention.

There is known a `device for adding aluminium to pigiron, which is formed by a chamber which is closed at the top and is to be heated by a burner. This chamber is provided at its side with a supply pipe with a syphon for maintaining a constant and calm level on the bottom of the chamber. In the bottom, there is an overflow provided about a central drainage channel, the inlet portion of which has a gradually narrowing transverse cross-section and the bottom of which shows a widened orifice. Under this, there is positioned a collector vessel having a discharge pipe at its side. This collector vessel is also closed on all sides and can be heated by a burner. A feeding chute for the additional material is provided through the cover of the chamber, which chute is coaxial to the drainage channel and reaches up to the overflow. The molten mass is supplied through the syphon in order to ensure that there will always issue a hollow, free-falling tubed stream from the drainage channel. Within the hollow of this tubed stream the additional material is supplied from the feeding chute as a free falling, independent core stream, which is not united to the tubed stream until far below the orifice of the drainage channel, substantially at the height of the bath level in the collector Vessel. This device cannot be used if magnesium or its preliminary alloys are employed, because, as the applicant has found, it entails serious danger from explosions.

Further, there is known a device for adding lead to iron alloys. This device is mounted on a steel ladle having a bottom provided with a drainage channel which can be closed by a stop rod. The device is formed by a storage container for the additional material(s), which is connected with a bore of the stop rod, which passes into a cylindrical chute extending into the drainage channel. The stop rod can seal on a conical seat in the drainage channel, or in a lifted position it can let a ring-like tubular stream of liquid metal flow into the further cylindrical part of the drainage channel, whereby a core stream of additional material can be fed through the chute.

By making the feeding chute of heat-resistant and insulating material and providing the stop rod at the upper side with a closing device, or by maintaining a high pressure in the bore of the feeding chute with the aid of gas or air, penetration by the molten mass of metal from the tubular stream intothe feeding chute, there to form a lump of frozen fast sintered metal which obstructs the further supply of additional material, may be avoided.

When using magnesium and its preliminary alloys this device has also proved to be useless on account of the occurrence of explosions.

The object of this invention is to provide a device which is of course free from the drawbacks referred to and which is perfectly reliable and will remain so for a long time. To this end there is according to this invention provided, in the bottom of a storage chamber for the melt, a mouth piece comprising an outlet channel having transverse cross-sections gradually decreasing towards the oritice and which has substantially no cylindrical part, and mounted concentrically within this outlet channel a cylindrical feeding chute for the additional material, the prefrably bevelled lower rim of the said chute-projecting from under the orifice of the outlet channel.

According to this invention, the lower rim projects by more than a quarter of the diameter of the orifice of the outlet channel and the diameter of this lower rim is about one half of the diameter of the orifice.

In a device according to this invention there arises a free-falling, closed tubular stream, which contracts about the lower rim of the feeding chute without being able to penetrate thereinto. It appears that hereby the surface tension in the stream is strong enough to receive the increase in pressure caused by the evaporation of the additional material into the core stream, without the stream exploding, whereas in the absence of a core stream the liquid metal does not penetrate into the feeding chute and obstructs it.

In view of this it is surprising to see the particularly homogeneous distribution obtained in the `melt bath and in the castings.

lf by some cause or other the lower rim of the feeding chute is worn or breaks off until far below the given value and comes to lie at substantially the same level with the orifice of the drainage channel, there will almost immediately occur obstructions and explosions, by which the feeding chute is ung out of the outlet channel.

Therefore, the feeding chute is preferably suspended so as to be readjustable, so that its lower rim can always be brought back to or be maintained at the right height to keep up with progressive wear.

An embodiment of a device according to this invention is hereinafter described with reference to the accompanying drawing, in which the figure is a transverse crosssectional view, partially schematic, showing an embodiment of the invention.

According to the figure, a mouth piece 2 of graphite is provided in the bottom 1 of a storage chamber to which the mass of molten metal is Iadded. The mouth piece block 2 is provided with an outlet or drainage channel 3, the transverse cross-section of which gradually and progressively narrows toward and up to its lower end, so that it is substantially without a cylindrical part.

A feeding chute 4 of graphite is mounted concentrically in the outlet channel 3 with the aid of a carrier 5 of graphite, which is centered in upstanding projections 6 of the block 2. Between the projections 6 and the carrier 5 there are formed gates 7, through which the melt from the storage chamber can enter the drainage channel 3.

The feeding chute 4 extends through the orifice 8 of the drainage channel 3 and the lower rim 9 of the feeding chute extends beyond the orifice 8 over a length, which is about equal to one third of the diameter of t-he said orifice, that is into the free-falling and freely contracting stream 10 of liquid metal of the melt. Towards its lower end, the feeding chute 4 narrows from the outside and widens from the inside, and the diameter of the lower rim 9 then is about half the diameter of the orifice 8.

From a storage hopper 11, the additional material falls into the feeding chute, 4 which can be kept at the right height with the aid of a heavy clamping holder 12 provided about the feeding chute 4 and which is thereby at the same time safeguarded against rising. Moreover, with the aid of this clamp it is possible to control the length of the projecting piece of the chute, by adjusting it to a higher or lower position.

A conical cavity 13 is created under the lower rim 9 in the freely contracting tubular stream 10, in which cavity the falling particles of additional material 14 are caught before they are taken up into the stream 10 which has then become one massive whole. Up to the cavity 13, the additional material is free from t-he direct radiation of the melt and remains cool.

In a test plant, use was made of an orifice diameter of 36 mm. and a lower rim diameter of 18 mm., which projected about 12 mm. ybelow the orifice 8. With this device, it proved to be possible to obtain a capacity of tons/hour.

In some experiments, 450 kg. 3.7% C., 1.2% Si, 0.3% Mn, less than 0.1% P and 0.045% S were introduced into the storage chamber of the device and were treated with 9 kg. of Ferro-Silicium- Magnesium Mg). The additional material conof cast iron containing tained 6 kg. having a grain size of 0.4-5 mm. and 3 kg. having a grain size of less than 0.4 mm. The adding operation took seconds and the reaction was not marked by any particularly brisk development. An examination of test pieces, both such as were cast directly after treatment and such as were cast after 10 minutes standing time, showed how a completely homogeneous spherical separation of Igraphite had arisen.

In a test immediately following upon this, 300 kg. of cast iron of the same composition were treated with 4.3 kg. of a mixture of Fe-Si-Mg grains and pure magnesium, about 1.3 kg. of which consisted of pure magnesium. This treatment took about 60 seconds and the development of the reaction was somewhat brisker. Here too, the graphite was separated completely in spherical form and evenly distributed.

After this, 340 kg. of cast iron were treated with 4.45 kg. of additional material, in which 9%: of the totally required amount of Fe-Si-Mg had been replaced by pure magnesium in granular form. The treatment took 83 seconds and the reaction developed, as was to be expected, in a much brisker way than in the previous experiments. However, no iron spattered from the ladle, into which the pouring `from the storage chamber was effected and the stream remained closed. The graphite was again completely separated in the spherical form.

When this experiment was repeated, the same result was achieved.

Eventually, an experiment was made with 450 kg. of cast iron having a temperature of about 1425 degrees centigrade with 5.1 kg. of pure granulated magnesium. The adding operation took 65 seconds. A little iron spattered from the ladle, but this was well within the limits of the permissible. The graphite had been separated practically entirely in the nodular form, with only a few crab formings.

When experiments were made with a device, in which an extension piece of 40 mm. length had been provided under the orifice 8, whilst the transverse cross-sections of the drainage channel being in conformity to the contracting stream, so that no free contraction occurred, the feeding chute would be sintered shut if ferrosilicium was used. The magnesium would also obstruct the chute, but directly afterwards the device was destroyed by an explosion.

In a device, in which a cylindrical extension piece of 40 mm. had -been provided under the orifice 8 conformably to the dotted line in the figure, a number of minor explosions` occurred when magnesium was used, by which explosions the liquid metal as well as the magnesium grains were flung far and wide, after which the feeding chute was partly sintered shut.

As has been ascertained by experiments, it is also possible, with the device according to the invention, successfully to add other additional materials to a mass of molten metal.

I claim: 1. In combination with a container for molten metals, a device for feeding additive materials into a stream of the molten metals, which additive materials have lower boiling points or lower specic weights or both than the molten metals, said device comprising, in combination:

means disposed in the bottom of said container and forming an annular outlet channel for the molten metal stream, the lowermost portion of said outlet channel forming an orifice, said outlet channel having a transverse cross section which narrows progressively toward and up to said orifice; and means forming a cylindrical feeding chute for said additive materials and extending from within said container substantially coaxially through said outlet channel, said feeding chute being made of heat-resistant material and extending past said orifice to terminate in a lower rim.

2. A device as defined in claim 1, wherein the distance between the lower rim and the orifice is at least one quarter of the diameter of the orifice.

3. A device as defined in claim 2, wherein the diameter of the lower rim is approximately equal to one-half the diameter of said orifice.

4. A device as defined in claim 3, wherein said lower rim of the feeding chute is bevelled.

5. A device as defined in claim 4, wherein the outer wall of the feeding chute is bevelled.

6. A device as defined in claim 3, including means for adjusting said distance between the lower rim and the orifice.

7. A device as defined in claim S, wherein at least One element in said combination is made of graphite.

References Cited I. SPENCER OVERHOLSER, Primary Examiner.

E. MAR, Assistant Examiner.

UNITED STATES PATENT QFEICE CERTIFICATE 0F CORRECTION Patent Ne'. 3,357,692 December 12, 1967 Hermanus Bakkerus It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

In the heading ito the Aprinted specification, line l0, for "Oct 14 1964" read Oct. l5 1963 Signed and sealed this 31st day of December 1968.

(SEAL) Attest:

Edward M. Fletcher, Jr. EDWARD J. BRENNER Attesting fficer Commissioner of Patents 

1. IN COMBINATION WITH A CONTAINER FOR MOLTEN METALS, A DEVICE FOR FEEDING ADDITIVE MATERIALS INTO A STREAM OF THE MOLTEN METALS, WHICH ADDITIVE MATERIALS HAVE LOWER BOILING POINTS OR LOWER SPECIFIC WEIGHTS OR BOTH THAN THE MOLTEN METALS, SAID DEVICE COMPRISING, IN COMBINATION: MEANS DISPOSED IN THE BOTTOM OF SAID CONTAINER AND FORMING AN ANNULAR OUTLET CHANNEL FOR THE MOLTEN METAL STREAM, THE LOWERMOST PORTION OF SAID OUTLET CHANNEL FORMING AN ORIFICE, SAID OUTLET CHANNEL HAVING A TRANSVERSE CROSS SECTION WHICH NARROWS PROGRESSIVELY TOWARD THE UP TO SAID ORIFICE; AND MEANS FORMING A CYLINDRICAL FEEDING CHUTE FOR SAID ADDITIVE MATERIALS AND EXTENDING FROM WITHIN SAID CONTAINER SUBSTANTIALLY COAXIALLY THROUGH SAID OUTLET CHANNEL, SAID FEEDING CHUTE BEING MADE OF HEAT-RESISTANT MATERIAL AND EXTENDING PAST SAID ORIFICE TO TERMINATE IN A LOWER RIM. 